The following description sets forth the inventor's knowledge of related art and problems therein and should not be construed as an admission of knowledge in the prior art.
As a photosensitive drum substrate for use in a photoelectrographic device, a substrate in which a photosensitive layer of, e.g., OPC (organic photoconductor) is formed on an external peripheral surface of a cylindrical aluminum pipe has been used. To attain excellent image quality, the photosensitive layer of the photosensitive drum is required to be thin and uniform in thickness with a high degree of accuracy, which in turn requires an aluminum pipe as the base material to have a surface high in smoothness.
As an aluminum pipe for such photosensitive drum substrate, an extruded aluminum pipe obtained by drawing an extruded aluminum raw pipe (hereinafter referred to as “ED pipe”) has been popularly used.
Such ED pipe may sometimes have defect protrusions caused by aluminum slugs (Al slugs) which adhered to the surface of the pipe during the extrusion process. Therefore, there is a report that such ED pipe causes image defects due to the defect protrusions when used as a photosensitive drum substrate as it is.
In view of the problems, in cases where such ED pipe is used as a photosensitive drum substrate, to prevent generation of defect protrusions, the external peripheral surface is popularly subjected to cutting work to obtain a mirror finished surface to thereby enhance the surface smoothness.
However, surface modification processing such as cutting work is insufficient, resulting in deteriorated productivity and increased production cost.
Under circumstances, there are many proposals regarding technique for employing a non-machined ED pipe as a photosensitive drum substrate.
For example, Japanese Unexamined Laid-open Patent Publication No. H08-82939 (hereinafter referred to as “Patent Document 1”) proposes a method for producing an aluminum pipe in which a surface of an ED pipe is wiped (polished) with a clean cloth, etc., after the drawing processing.
Japanese Unexamined Laid-open Patent Publication No. 2004-9227 (hereinafter referred to as “Patent Document 2”) proposes a method for producing an aluminum pipe in which a surface of an ED pipe is polished with polishing agent after the drawing processing.
Furthermore, Japanese Unexamined Laid-open Patent Publication No. H05-313394 (hereinafter referred to as “Patent Document 3”) proposes a method for producing an aluminum pipe in which a certain thickness of an external peripheral surface of an extruded aluminum raw pipe is removed by cutting, etching, blasting, polishing, etc., before the drawing processing.
In the method for producing an aluminum pipe as disclosed by Patent Documents 1 and 2 in which a surface of an aluminum pipe is subjected to polishing or the like to improve the surface smoothness after the drawing processing, this method performs a surface modification like the method employing a cutting work. Therefore, the method is not only inefficient and but also hard to fundamentally solve problems such as deteriorated productivity and increased producing cost.
On the other hand, in the method for producing an aluminum pipe as disclosed by Patent Document 3, since a surface of an aluminum pipe is removed evenly before the drawing processing, there is a possibility that the removed slugs (aluminum slugs) re-adheres to the surface of the aluminum raw pipe to cause defect protrusions due to the removed slugs after the drawing processing, resulting in image defects by the defect protrusions. Thus, it was difficult to attain high quality. Furthermore, in this method, since the surface of the aluminum raw pipe is removed by a certain thickness, the surface removing causes a decreased diameter. As a result, it becomes difficult to control the pipe diameter, which in turn may cause deterioration of the quality due to the deteriorated dimensional accuracy.
The description herein of advantages and disadvantages of various features, embodiments, methods, and apparatus disclosed in other publications is in no way intended to limit the present invention. Indeed, certain features of the invention may be capable of overcoming certain disadvantages, while still retaining some or all of the features, embodiments, methods, and apparatus disclosed therein.
Other objects and advantages of the present invention will be apparent from the following preferred embodiments.